为薄膜应用优化基于ZrO2和HfO2的初始铁电体中的压电应变：从头算起掺杂剂筛选研究。,ACS Applied Materials & Interfaces

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为薄膜应用优化基于ZrO2和HfO2的初始铁电体中的压电应变：从头算起掺杂剂筛选研究。
ACS Applied Materials & Interfaces ( IF 8.3 ) Pub Date : 2020-06-15 , DOI: 10.1021/acsami.0c08310
Max Falkowski ₁ , Alfred Kersch ₁

Affiliation

HfO ₂和ZrO ₂作为铁电，热电和压电应用中薄膜的无铅且与硅技术兼容的材料越来越引起研究人员的兴趣，这些薄膜用于铁电场效应晶体管，铁电随机存取存储器，纳米级传感器和能量收集器。由于针对含铅电子元件的环境法规，HfO ₂和ZrO ₂与AlN，（K，Na）NbO _3-和（Bi _0.5 Na _0.5）TiO ₃基材料一起提供了Pb（Zr）的替代品。_x Ti _{1– x}）O ₃基材料，在工业中是绝大多数使用的陶瓷。HfO ₂和ZrO ₂薄膜可能显示出场致相变，从顺电四方相转变为铁电斜方相，从而导致晶体体积变化，从而引起应变。这些场致应变已经在纯掺杂系统中进行了实验测量；然而，无论是实验还是理论上，都没有对压电活性进行系统的优化。在这项筛选研究中，我们根据氧气的供应和缺陷掺入类型（替代或间隙）来计算58种掺杂剂的最终效应大小。在ZrO _2中使用Yb，Li和Na可获得最大的压电应变值并且超过40 pm V ^–1或最大应变的0.8％，超过最佳实验结果的2倍。此外，我们发现Mo，W和Hg使ZrO ₂的极性斜方晶相在一定条件下稳定在这种情况下，陶瓷结晶过程将有利于这些系统。我们的工作通过合理设计基本机制来指导有前途的材料系统性能的发展，以便将其应用于不可预见的应用中。

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Optimizing the Piezoelectric Strain in ZrO2- and HfO2-Based Incipient Ferroelectrics for Thin-Film Applications: An Ab Initio Dopant Screening Study.

HfO₂ and ZrO₂ have increasingly drawn the interest of researchers as lead-free and silicon technology-compatible materials for ferroelectric, pyroelectric, and piezoelectric applications in thin films such as ferroelectric field-effect transistors, ferroelectric random access memories, nanoscale sensors, and energy harvesters. Owing to the environmental regulations against lead-containing electronic components, HfO₂ and ZrO₂ offer, along with AlN, (K,Na)NbO₃- and (Bi_0.5Na_0.5)TiO₃-based materials, an alternative to Pb(Zr_xTi_1–x)O₃-based materials, which are the overwhelmingly used ceramics in industry. HfO₂ and ZrO₂ thin films may show field-induced phase transformation from the paraelectric tetragonal to the ferroelectric orthorhombic phase, leading to a change in crystal volume and thus strain. These field-induced strains have already been measured experimentally in pure and doped systems; however, no systematic optimization of the piezoelectric activity was performed, either experimentally or theoretically. In this screening study, we calculate the ultimate size of this effect for 58 dopants depending on the oxygen supply and the defect incorporation type: substitutional or interstitial. The largest piezoelectric strain values are achieved with Yb, Li, and Na in ZrO₂ and exceed 40 pm V^–1 or 0.8% maximal strain, which exceeds the best experimental findings by a factor of 2. Furthermore, we discovered that Mo, W, and Hg make the polar-orthorhombic phase in the ZrO₂ bulk stable under certain circumstances, which would count in favor of these systems for the ceramic crystallization process. Our work guides the development of the performance of a promising material system by rational design of the essential mechanisms so as to apply it to unforeseen applications.

更新日期：2020-07-22

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